It is known to provide a bottom bracket bearing arrangement for journaling an axle carrying the crank arms to which, in turn, respective pedals are pivotally connected for a bicycle.
In general, steel bearing balls serve to journal the axle in a bearing sleeve which can be accommodated in the bottom bearing bracket.
Bottom bracket bearing units of the aforedescribed type are described in German open application DE-OS 34 07 120 and DE-OS 34 34 314. Such systems permit simple assembly of the bottom bracket bearing unit in the bottom bracket of the bicycle frame since the entire bearing structure can be received in the installation sleeve which fits into the housing of the bottom bracket. The mounting operation merely involves connecting the two parts of the installation sleeve in the bottom bracket.
The installation sleeve may comprise a long sleeve member flanged at one end and engaging at its other end, e.g. received within a short flanged sleeve with the flanges of the two sleeves bearing upon opposite axle ends of the receiving housing of the bottom bracket. In general, at each end of the installation housing, a crown of bearing balls is provided which ride upon metallic and, generally, steel bearing shells or races which, as a rule, have a quarter circular arcuate ring profile.
The installation and mounting of such ball bearings and the respective races involve considerable expense and effort.
The same holds true for other known bottom bracket bearings in which the balls form circular rows of ball bearings which ride in races formed as grooves in the shaft or axle and in cylindrical bearing shells or races fitted into or embedded in the plastic or synthetic resin installation sleeves.